Circuit control device



March 29, 1938. w. LpSMlTH 2,

CIRCUIT CONTROL DEVICE I Filed Oct. 1, 1935 2 Sheets-Sheet l 63M fIEVENTOR March 29, 1938. w,- sMlTH 2,112,716

CIRCUIT CONTROL DEVICE AITORNEY Patented -Mar. 29, 1938 UNITED STATES.

PATENT. OFFICE CIRCUIT CONTROL DEVICE Application October 1, 1935, Serial N0. 43,030

10 Claims.

1 This invention relates to improvements in the operation of heating devices, welding machines and similar devices having automatic operation wherein a certain sequence of operation is desired.

The invention relates more particularly to spot welding machines in which the electrodes are forced against the work-piece under pressure and in which it is desired to have the electrodes in electrical contact with the work-piece prior to the turning on of the weldingcircuit.

It is necessary in the functioning of a welder, such as a spot welder which is operated at very high speed, that'in each succeeding operation, the electrodes be in electrical contact with the "work-piece beforethe welding current'is applied to the electrodes, in order to prevent the burning of the electrodes and the work-piece.

In the past, pressure switches have been used for this purpose. Pressure being applied to a piston, it moves quickly so as to clamp the electrodes on the work-piece. This clamping stops the movement of the piston. The pressure then builds up to the normal amount, operating the pressure switch which closes the welder contactor. v I

In practical use, it has been found that due to the inertia of the moving piston or due to a high return spring pressure, the pressure may build up in the pipe line" to the normal amount before the piston starts to move, causing the pressure switch to act, closing the contactor before the piston' has actually caused the electrodes to clamp on, the work-piece; This premature closing of the welder contactor is likely to cause severe burning of the electrodes and the workpiece when these are clamped together with the electrodes energized.

It is therefore a principal object of this invention to provide a simple effective means to prevent premature closing of the welder contactor and which shall cause closing of this contactor consequent upon the actual contact made by the electrodes on the work-piece.

Another object of thisinvention is to insure the correct sequence of events in theprocess of applying the electrodes. to the work-piece followed by the energization of the welding .circuit. A further object of this invention is to secure automatic operation or the circuits of a heating or welding machine, thereby securing correct operation as to the sequence of steps of operation, without the attention of an operator.

Other objects will appear as my inventionis described hereinafter.

In the drawings accompanying this specification and forming a part of this application, I have shown for purposes of illustration, certain embodiments which my invention may assume and in these drawings,'-- I Fig 1 is a schematic diagramof one embodiment of my invention. 1

Fig. 2 is a similar diagram of another embodiment of my invention.

Fig. 3 is a modification in part of one of the circuit members of either of Figs. 1 or 2 The embodimentof my invention'disclosed in Fig. 1 includes the schematic showing of such an arrangement of parts of a spot welding machine (not completely shown) comprising an inlet fluid conduit 5|, an outlet fluid conduit' 52, a -,control valve 32 which controls the flow of fluid in the conduits 5| and 52, a movable electrode 53, and a stationary electrode 54. -The movable electrode 53 is moved by fluid in the cylinder 50 Q against a spring 51 into engagement with the work-pieces 55, here shown also in engagement with the stationary electrode 54.

Included in the work circuit is shown a weld-,- ing transformer 40 having a primary winding 39 and a secondary winding 38. The movable electrode 53 is connected to the secondary winding 38 through conductor 56, and the stationary conductor 54 is connected to the secondary winding 38 through the conductor 3|.

When a source of supply is connected to supply lines I and 2, there is a circuit energized from the supply line I through conductor 3, primary winding 39, of the welding transformer 30, conductors 62 and9, normally closed contacts ll, of a timer 33, resistance l9, preferably variable, winding I! of relay switch 35, conductor ID, to an intermediate tap of auto-transformer", conductor 2| to the supply line 2, this circuit to be known. as the relay circuit.

Another circuit is energized upon the applicationof a source of energy to the supply lines, including supply line I, conductor H, auto-transformer 20, conductor 2| to the supply line 2. This circuit is herein referred to as the autotransforr ner circuit.

Due to the impedance of the primary winding 39 of the welding transformer 40, suflicient current does not flow through the winding ll of relay 35 to close its contacts it. Thus the main work circuit is not yet closed.

The closure of a push button energizes a winding 26 of a relay 36 by the completion of a circuit from the supply line .i through push button 25, conductor 23, winding 25 of relay 36,

conductor 21 to the supply line '2. This circuit is referred to as the push button circuit.

The energization of the winding 26 of the relay 36 closing its contacts I2, completes the circuit from supply line I through the push button 25, conductors 23 and 24, contacts I2 of .relay 36, conductor 28 winding 29 of valve 32, conductor '36 to a supply line 2. This energization of the winding29 operates the valve 32 against a compression spring I5, closing the outlet fluid con-. duit 52 and opening the inlet fluid conduit 5|,

allowing the pressure to enter the cylinder 56, thereby causing the movable electrode 53 to move againsta spring 51 into electrical contact with the work-pieces 55 located between the electrodes 53 and 54, and thereby causing a short circuit .of the secondary winding 38 of the welding transformer 46.

' Short circuiting this secondary winding 38 of the welding transformer 46 reduces the impedance of primary winding 39 of transformer '46, allowing suiiicient current to flow through the -Winding I1 of relay 35, to energize it sufiiciently to close its normally open contacts I6.

Closure of the contacts I6 of relay 35 completes a circuit from supply line I, conductor 4,

- contacts I6 of relay 35, conductor 5, winding 6 of the main workcircuit switch 6I, conductor 1 to the supply line 2. the energization circuit for the welding switch. The energization of the winding 6 of the welding switch 6| causesthe closure of contacts 66 and I 6. Closure of-contacts 66 completes the work circuit, whereupon the period of welding begins. 7

This circuit includes the supply line I, conductor 3, primary winding 39 .of .welding transformer-46, conductor 62, contacts 66 of main switch 6I, conductor 8 to the supply line 2.

The closure of contacts 66 of the welding switch 6| also closes a holding circuit for the.winding I1 of relay -35,.from supply 'line I, conductor 11,

the left hand portion of the auto-transformer winding 26 to the tap 16, conductor I8, relay winding I1, resistance I9, timer contacts I4, conductor 9, contacts 66 of the main welding switch 6I, conductor 8, to the supply line 2.

This is to insure the continuance -of the energization of winding I1 of relay 35 from the time of closing of the contacts 66 of the main switch 6| until the opening of the timer contacts I4. A

' Closure of contacts I6 of the main switch 6| completes a holding circuit for the said push button circuit, insuring acontinuance of the closure of contacts I2 of relay 36, and permitting the push button 25 to be released. This holding. circuit includes conductor I3 from the supply line I, contacts I6 of welding switch 6|, conductor II,

contacts I2 of relay 36, conductor 24, winding 26 of relay 36, conductor 21 to the supply line 2.

The welding period continues until the actuation of the timer 33 opens its contacts I4, which opens the work circuit, and the opening of the contacts IU of the main welding switch 6| opens the holding circuit'of the winding 26 of relay 36.

The push button25 having been opened previously, the circuit through winding 26 of relay 36 being now opened, causes a deener'gization of the winding 26, opening the contacts I2 and dey This circuit is herein called energizing the winding 29 of control valve 32,

permitting the spring I5 to return the valve 32 to the position shown. I

The return movement of valve 32 releases the pressure in the cylinder 56, whereby the movable electrode 53 is moved away from the workpieces 55 and the stationary electrode 54 by the spring 51. I

At this time .all the circuits being opened excepting that of the relay circuit and that of the.

considerable amount of power compensates for any changes made in the position of the tap of the primary winding I29 so that the operating characteristics of the relay III may remain the same as those of the-circuits heretofore described in connection with Fig. l.

With the application of a source of energy to -the supply lines I6I and I62 no circuit is as yet.

completed. In this respect the arrangement difiers from the embodiment illustrated in Fig. 1. In Fig. 2 the closure of push button I25c0mpletesthe push button circuit from supply line I6I through push button I25, conductor I96, contacts I35of relay I36, conductor I9I, winding I14 of relay I24, conductor I3I to supply line I62.

This push button circuit energizes the winding I14 of relay I24, closing the normally open contacts I31 and I23 of the relay I24. A holding circuit is provided for the push button circuit in order to insure a continued energization of the winding|14 of relay I24 included insaid circuit during the welding period, permitting the push button to be released, the holding circuit being from supply line I6I, conductor I45, contacts I31 of relay I24, conductors I46 and I96, contacts I 35 of relay I36, conductor 'I9I, winding I14 of relay I24, conductor I3I to the supply line I62.

Closureof contacts I31 completes a circuit, energizing the-winding I86 of the control valve I81 by'a circuit from the supply line I6I, conductor I45,'contacts I31 of relay I24, conductorsI46, I28, winding I86 of this controlvalve l81, and a conductor I36 to the supply line I62. The energization of the winding I14 of relay I24 closing contacts I23 also completes an energization circuit "for, the auto-transformer I26 from supply line I6I, conductor I2I, auto-transformer I26,

conductor I22, contacts I23 of relay I24, conductors I92, I3I to supply line I62,

By the actuation of control valve I81, pressure enters the cylinder I 85, moving-the electrode I86 toeflect electrical contact with the work-pieces I8I and the stationary electrode I82.

Also at the-time of the closure of contacts I23 by the energization of the winding I14 of the relay I24, the relay circuitis completed from the supply line I6I, conductor I63, primary winding I29 of welding transformer I16, conductors I and I61, winding II6 of relay III in parallel with the reactor II4, conductor 5, to the intermediate tap of auto-transformer I26, conductor I22, contacts I23 of relay I24, conductors I92 and .I3I, to supply line I62.

The primary winding I29 of the transformer I16 acting as an impedance device retards the 7b current passing through the relay circuit and prevents the operation of relay III. However, upon the completion of the secondary circuit of the transformer I18 by the bringing of the electrodes I80 and I82. into electrical contact with the workp'iece I8I, the impedance is reducedmaterially, thus allowing sufllcient current to pass through the relay circuit, to energize the -winding IIO of relay 'III, and thus close coning-I53 of the welding switch I54 closes the contacts I51 of the welding switch and-starts the welding period by the completion of the work circuit from supply line IOI, conductor I03, primarywinding I23 of welding transformer I10, conductor I05, contacts I51 of main switch I54, conductor I56 to the supply line I02.

The welding period being completed, the nOl mally open contacts I33 of the timer (not shown) are closed, completing the timer circuit from thesupp y line IOI, conductor -I4I, contacts I33, con ductor I42, winding I260! relayl36, conductor I21 to the supply line I02, this timer circuit enerwinding I26, causing opening of the contacts I35 and the closure of contacts I 5| of relay I36.

The closure of contacts -I5I of relay switch I36 forms a holding circuit for the winding 1 I26 of the same switch from supply line IOI, conductor I, contacts I31.'of relay I24, conductors I40, I80, I38, contacts I5I of relay I36, conductors I39, I42, winding 'I26 of relay i36, conducto'r I21 to the supply line I02. The purpose of this holding circuit is to hold the relay I36 in operative position should the contacts I 33 of the timing device open before the winding I14 of relay I24 is completely deenergized and its contacts opened. g

The deenergization of relay I24 opens the contacts I31 and I23 of the same relay. The opening of contacts I31 opens the circuit to the main welding switch I54, causing deenergization of the winding I53 of the main welding switch, re-

. sulting in an opening of the contacts I51 which in turn open the work circuit, thus terminat-- lay I24 opens the-'auto-transformer circuit and the relay circuit and consequently deenergizes .the'winding IIO of relay III, thereby opening contacts I50.

At the expiration of the period during which the contacts I33 of' the timing device are to remain closed, the said contactsare then opened, I deenergizing the winding I26 of relay I36. The

apparatus is now 'in condition for the beginning of another welding operation, by the closure of the manually operated switch, or push button Instead of the autowtransformer 20 illustrated in Fig. 1, I may use a resistance device or potentiometer as shown. in Fig. 3 in which the conductor I8 is connectedto an intermediate tap 10,

and the conductors H and 2I are connected to the terminals of the resistance device. The autotransformer I20- illustrated in Fig. 2 may also be replaced by an arrangement such as illustrated in Fig. 3. Other well-known multiple circuit voltage supply devices may be used instead of the auto-transformer, or the resistance device, here shown and described.

The intermediate tap 10 is shown adjustable,

so that there may be provided, if desired, a voltage of one value for the actuating circuit of the relay 35 of vF'ig. 1, or the. relay III of Fig. 2, and a voltage of a diiierent value for the holding circuit of these relays.

It will be noted that the actuating circuit of the relay includes one portion 015 the autotransformer, or resistance device, and that the holding circuit includes another portion thereof. The holding circuit as shown also includes the main welding circuit contacts of the welding switch.

The timer I 33 of Fig. 2 may be any automatic timer such as described in the applications of D. C. Wright, United States Letters Patent No. 2,023,631, issued December 10, 1935, and United States Letters Patent No. 2,024,019, issued De-.;

cember 10, 1935. Y

Havingthus described my invention, what I claim is: v I

1. An apparatus for controlling the flow of electrical energy to a welding circuit including electrodes arranged for receiving work pieces to be welded therebetween, comprising a primary circuit connectible to a source of current and including a primary winding, a secondary winding in inductive relation to the primary winding, and electrically connected to the electrodes,

a control circuit electrically operatively associated with the primary circuit, multiple voltage supplymeans electrically operatively associated with the primary winding for supplying a predetermined voltage thereto, and means operated by the control circuit at a predetermined ener gization thereof for altering the association of said multiple voltage supply means and said primary winding for supplying a different voltage to said primary winding, said predetermined energization of the control circuit being provided by the change in impedance in the primary winding itself caused by and at the instant of the contact of the electrodes with the work pieces.

2. An apparatusfor controlling the flow of;- electrical energy to a welding circuit including electrodes arranged for receiving work pieces to be welded therebetween, comprising a primary circuit connectible to a source of current and including a primary winding, a secondary winding in inductive relation to the primary winding and. .electrically connected tothe electrodes, a control circuit electrically operativelyassociate'd with the primary circuit, voltage reducing means electrically operatively associated with the primary winding, and means operated by'the control cir-- cuit at a predetermined ener'gization thereof for rendering said voltage reducing means ineifec-' tive. withrespect to the primary winding, said predetermined energization of the control circuit being provided by the change in impedance in the primary winding caused by and at the instant of the combined contact of the electrodes with. the

electrodes arranged for receiving work pieces to be welded therebetween, comprising a primary winding connectible to a source of current, a secondary winding in inductive relation to the primary winding and electrically connected to the electrodes, multiple voltage supply means electrically operatively associated with the primary winding for connecting the winding to the source therethrough in addition to the first mentioned connection of the primary winding to said source, a control circuit electrically operatively associated with the prima'ry winding and ener'gizable through one portion of said multiple voltage supply means, a holding circuit energizable through a second portion of said multiple voltage supply means, switch means operable at a predetermined energization of the control circuit for effecting said first mentioned connection between said primary winding and saidsource and for rendering said multiple voltage supply means ineffective with respect to the primary winding, said first mentioned connection of said primary winding to said source causing'energization of said holding circuit for maintaining said switch means in operative position, said predetermined energization of the'control circuit being caused by the change in impedance in the primary winding itself caused by the contact of the electrodes with the work pieces.

4,. An apparatus for controlling the flow of electrical energy to a welding circuit including electrodes arranged for receiving work pieces to be welded therebetween, comprising a primary winding connectible to a source of power, a secondary winding in inductive relation to the primary winding and electrically connected to the electrodes, voltage dividing means electrically operatively associated with the primary winding for connecting the winding to the source therethrough in addition to the first mentioned connection of the primary winding to said source-a control circuit electrically operatively associated with the primary winding and energizable from one portion of said voltage dividing 'means, a holding circuit energizable from a second portion of said voltage dividing means, and switch means operable at a predetermined energization of the control circuit for efiecting said first mentioned connection between said primary circuit and said source, the said first mentioned connection of said primary winding to said source causing energization of said holding circuit for maintaining said switch means in operative position, said predetermined energization of the control circuit being caused by the change in impedance in the primary winding itself caused by the contact of the electrodes with the work pieces.

5. Anapparatus for controlling the flow of electrical energy to a translating device, comprising a primary circuit connectible to a source ofv power and including a primary winding, a secondary winding in inductive relation to the primary winding and electrically connected to theelectrodes, voltage dividing means connected to said source of power and electrically operatively associated with the primary circuit for supplying a predetermined voltage thereto, a

control circuit electrically operatively associated with theprimary winding'and energizable from one portion of said voltagedividing means, a holding circuit energizable from a second portion of saidvoltage dividing means, and switching means operable at a predetermined energize tion of the control circuit for altering the association of said voltage dividing means with said primary circuit while the voltage dividing means remains connected to the primary winding for supplying a different voltage to said primary winding, the altering of theassociation of said voltage dividing means with said primary circuit causing energization oi? said holding circuit for maintaining said switching means in operative position, said predetermined energiz'ati'on of the control circuit being eifected by the change of impedance of the primary winding caused by operatively connecting said secondary winding to said translating device.

6. An apparatus for controlling the flow of electrical energy to a welding circuit including electrodes arranged for receiving work pieces to be welded therebetween, comprising a primary winding, voltage reduction means in series there- 'with, a circuit connecting said winding through and with said voltage reduction means, control means operated by the control circuit when energized to an increased degree to shunt out said voltage'reduction means from its series relationship with the primary winding, said control circuit being energized sufllciently for operating said control means at the instant of the combined contact of the electrodes with the work pieces.

, 7. The combination with an apparatus for controlling the ilowof electrical energy to an electrical energy translating device and including a primary winding subjected to a predetermined potential from a source of electrical energy and a secondary winding in inductive relation to the primary winding and connectible to the translating device, of means rendered operative by the change in the impedance of the primary winding resulting from operatively connecting said secondary winding to the translating device for subjecting the primary winding to a different predetermined potential, said means at all times being connected with said primary winding in permajustment of the primary winding for controlling the energization of the primary, winding, of an inductive reactance connected in parallel with said winding of said device for rendering said winding operative through substantially the entire range of adjustment of the primary winding.

9. In an electrical power circuit and control circuit combination, operating means for conmeeting and disconnecting the power circuit to andfrom a source of power, an operating circuit, aholding circuit, said circuits being operatively ,associated' with the operating means for initially operating said means to connect the power circuit across the source of power and to maintain said connection, respectively, voltage dividing means connected continuously across said source of power, the operating circuit being operatively associable with said source of power through one portion of said voltage dividing means for initially operating the operating. means, and the holding circuit being operatively associable with said 75 source of power through the other portion of the voltage dividing means for maintaining said operating means in operated position and Being rendered operative consequent upon connecting said power circuit across said source of power.

10. In a combined operating and holding circuit for an electro-responsive control device for controlling an electro-responsive operating device, circuit closing means operatively associated with the operating device, voltage dividing means, connectionswhereby said electro-responsive control device is operated by completion of a circuit across one portion of said voltage dividing means, operation or said control device causing operationof the electro-responsive operating device and consequent closure of the associated circuit closing means, said closure resulting in the maintenance 01' a 'holding circuit for said electro-re sponsive control device across another portion of said voltage dividing means.

WARD L. SMITH. 

